Global Hall-magnetohydrodynamic simulations of transition disks

Abstract

Context. Transition disks (TDs) are a type of protoplanetary disk characterized by a central dust and gas cavity. The processes behind how these cavities are formed and maintained, along with their observed high accretion rates of $10^{-8} -10^{-7} \, M_{\odot} \, \mathrm{yr}^{-1}$, continue to be subjects of active research. Aims. This work aims to investigate how the inclusion of the Hall effect (HE) alongside Ohmic resistivity (OR) and ambipolar diffusion (AD) affects the structure of the TD. Of key interest is the dynamical evolution of the cavity and whether it can indeed produce transonic accretion, as predicted by theoretical models in order to account for the observed high accretion rates despite the inner disk's low density. Methods. We present our results of 2D axisymmetric global radiation magnetohydrodynamic (MHD) simulations of TDs for which all three non-ideal MHD effects are accounted. We used the NIRVANA-III fluid code and initialized our model with a disk cavity reaching up to $R=8~\mathrm{au}$ with a density contrast of $10^5$. We performed three runs, one with only OR and AD, and one for each of the two configurations that arise when additionally including the HE, that is, with the field aligned (anti-aligned) with respect to the rotation axis. Results. For all three runs, our models maintain an intact inner cavity and an outer standard disk. MHD winds are launched both from the cavity and from the disk. Notably, when the HE is included, ring-like structures develop within the cavity. We moreover obtain accretion rates of $3 - 8 \times 10^{-8} \, M_{\odot} \, \mathrm{yr}^{-1}$, comparable to typical values seen in full disks. Importantly, we clearly observe transonic accretion ($v_{\mathrm{acc}} \gtrsim c_{s}$) in the cavity. Additionally, outward magnetic flux transport occurs in all three runs.